1. Field of the Invention
The invention relates to a method for traffic management in a radio system and a network element.
2. Description of the Related Art
The increasing number of users and density of mobile terminals together with the need for transferring large amounts of data further increase the demands set for the capacity and management of wireless communication systems. In the future, there will be more and more users of non-real-time (NRT) services, for example interactive users such as web browsers transferring large amounts of information and users transferring data associated with video and audio signals over wireless communication systems. Mainly for this reason, it has been proposed that future wireless communication networks should use several types of radio access technologies instead of just one type of technology, i.e. the use of multisystem networks.
In order to use multisystem or multicarrier (called also multiradio) networks efficiently, it is essential to utilize all the systems or carriers efficiently. Efficiency can be improved, for example, by using trunking, a technique by means of which the capacity of several radio channels is automatically distributed between several users. The trunking efficiency of a network can be improved by introducing load-balancing mechanisms between systems or carriers.
Multisystem radio traffic management is required to balance RT (real time) load and, naturally in pursuance also interference, evenly between cells, thus maximizing the trunking efficiency. For non-real time services in turn the purpose of multiradio traffic management is to balance the NRT load (and/or interference) evenly between cells and thus to maximize the throughput i.e. to minimize the delay experienced by a user. In multisystem environment, trunking gain can be achieved, for example, by directing an RT user and/or NRT user to another system, or to another layer or frequency when the load is heavy thus reducing blocking. A NRT user can also be directed to an adjacent cell of the same layer or system. When real-time services are concerned, directing is typically called handover (HO) but it can also be called network controlled cell reselection (NCCRS).
In the prior art the cell load of the radio cells in a radio system has typically been measured by monitoring occupation of physical resources, interference or throughput or buffer delays. There are, however, several disadvantages associated with using throughput and/or delay measurements to measure NRT load. Especially, the calculation/mapping of delay/throughput values to actual nRT load is problematic mainly because it depends a lot on the system (GPRS/EGPRS, for instance). A problem is also that calculating and mapping depends a lot on the radio conditions (network scenario, frequency reuse, etc.). Additionally, the delay caused by network elements such as SGSN (serving GPRS support node) cannot necessarily be taken into account.